1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel that is capable of improving the discharge efficiency and the brightness. The present invention also is directed to a method for driving the plasma display panel.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture. Such a PDP is easy to be made into a thin-film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. Such a PDP is largely classified into a direct current (DC) type and an alternating current (AC) type. The DC-type PDP causes an opposite discharge between an anode and a cathode provided at a front substrate and a rear substrate, respectively to display a picture. On the other hand, the AC-type PDP allows an AC voltage signal to be applied between electrodes having dielectric layer therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Such a PDP typically includes an AC-type, surface-discharge PDP that has three electrodes as shown in FIG. 1 and is driven with an AC voltage.
Referring to FIG. 1, a scanning/sustaining electrode 16 and a common sustaining electrode 17 making a sustaining surface-discharge by an application of a AC driving signal are arranged, in parallel, at the rear side of an upper glass substrate 14 constructing the upper substrate 10. The scanning/sustaining electrode 16 and the common sustaining electrode 17 are transparent electrodes made from indium-tin-oxide (ITO), and metal bus electrodes 20 for supplying AC signals are formed, in parallel, on each of the scanning/sustaining electrode 16 and the common sustaining electrode 17. Because of a high resistance of the transparent electrode, a signal applied from a real external driver is applied, via the metal bus electrode 20, to the transparent electrode of each discharge cell. An upper dielectric layer 18 is entirely formed at the rear side of the upper glass substrate 14 provided with the scanning/sustaining electrode 16 and the common sustaining electrode 17. The upper dielectric layer 18 is responsible for accumulating electric charges during the discharge and limiting a discharge current. A protective layer 21 entirely coated on the upper dielectric layer 18 protects the upper dielectric layer 18 from the sputtering during the discharge to prolong a life of the pixel cell as well as to enhance an emission efficiency of secondary electrons, thereby improving a discharge efficiency. On a lower glass substrate 22 constructing the lower substrate 12, an address electrode 22 is arranged perpendicularly to the scanning/sustaining electrode 16 and the common sustaining electrode 17. A lower dielectric layer 26 for forming wall charges during the discharge is entirely coated on the lower glass substrate 22 and the address electrode 24. Barrier ribs 32 are vertically formed between the upper substrate 10 and the lower substrate 12. The barrier ribs 32 arranged, in parallel to the address electrode 24, on the lower dielectric layer 26 defines a discharge space 28 along with the upper substrate 10 and the lower substrate 12, and shut off an electrical and optical interference between the adjacent discharge cells. In order to minimize an interference between the adjacent discharge cells, the barrier ribs 32 may be formed in a direction horizontal to the address electrode 24 as well as in a direction vertical to the address electrode 24 to have a lattice-shaped structure. A fluorescent material 30 are coated on the surfaces of the lower dielectric layer 26 and the barrier ribs 32. The discharge space 28 is filled with a mixture gas of He+Xe or Ne+Xe.
Referring to FIG. 2, a driving apparatus for the AC-type PDP includes a PDP 40 in which m×n discharge cells 44 are arranged in a matrix pattern in such a manner to be connected to scanning/sustaining electrode lines Y1 to Ym, common sustaining electrode lines Z1 to Zm and address electrode lines X1 to Xn, a scanning/sustaining electrode driver 36 for driving the scanning/sustaining electrode lines Y1 to Ym, a sustaining electrode driver 34 for driving the common sustaining electrode lines z1 to Zm, and first and second address electrode drivers 38A and 38B for making a divisional driving of odd-numbered address electrode lines X1, X3, . . . , Xn−3, Xn−1 and even-numbered address electrode lines X2, X4, . . . Xn−2, Xn. The scanning/sustaining electrode driver 36 sequentially applies a scanning pulse and a sustaining pulse to the scanning/sustaining electrode lines Y1 to Ym, thereby allowing the discharge cells to be sequentially scanned line by line and allowing a discharge at each of the m×n discharge cells 44 to be sustained. The common sustaining electrode driver 34 applies a sustaining pulse to all of the common sustaining electrode lines Z1 to Zm. The first and second address electrode drivers 38A and 38B supplies an image data to the address electrode lines X1 to Xm in such a manner to be synchronized with the scanning pulse. The first address electrode driver 38A supplies the odd-numbered address electrode lines X1, X3, . . . , Xn−3, Xn−1 with an image data while the second address electrode driver 38B supplies the even-numbered address electrode lines X2, X4, . . . , Xn−2, Xn with an image data.
Such a PDP driving method typically includes a sub-field driving method in which the address interval and the discharge-sustaining interval are separated. In this sub-field driving method, as shown in FIG. 3, one frame 1F is divided into n sub-fields SF1 to SFn corresponding to each bit of an n-bit image data. Each sub-field SF1 to SFn is again divided into a reset interval RP, an address interval AP and a discharge-sustaining interval SP. The reset interval RP is an interval for initializing a discharge cell, the address interval AP is an interval for generating a selective address discharge in accordance with a logical value of a video data, and the sustaining interval SP is an interval for sustaining a discharge at the discharge cell 44 in which the address discharge has been generated. The reset interval RP and the address interval AP are equally allocated in each sub-field interval. A weighting value with a ratio of 20: 21: 22: . . . :2n−1 is given to the discharge sustaining interval SP to express a gray scale by a combination of the discharge sustaining intervals SP.
FIG. 4 is waveform diagrams of driving signals applied to the PDP during a certain one sub-field interval SFi. In the reset interval RP, a priming pulse Pp is applied to the common sustaining electrode. By this priming pulse Pp, a reset discharge is generated between each common sustaining electrode Zm and each scanning/sustaining electrode Y1 to Ym of the entire discharge cells to initialize the discharge cells. At this time, a voltage pulse lower than the priming pulse Pp is applied to the address electrode An so as to prevent a discharge between the address electrode An and the common sustaining electrode Zm. By the reset discharge, a large amount of wall charges are formed at the common sustaining electrode Zm and the scanning/sustaining electrode Y1 to Ym of each discharge cell. Subsequently, a self-erasure discharge is generated at the discharge cells by the large amount of wall charges to eliminate the wall charges and leave a small amount of charged particles. These small amount of charged particles help an address discharge in the following address interval. In the address interval AP, a scanning voltage pulse −Vs is applied line-sequentially to the first to mth scanning/sustaining electrodes Y1 to Ym. At the same time, a data pulse Vd according to a logical value of a data is applied to the address electrodes An. Thus, an address discharge is generated at discharge cells to which the scanning voltage pulse −Vs and the data pulse Vd are simultaneously applied. Wall charges are formed at the discharge cells in which the address discharge has been generated. During this address interval AP, a desired constant Voltage is applied to the common sustaining electrodes Zm to prevent a discharge between each address electrode An and each common sustaining electrode Zm. In the sustaining interval SP, a sustaining pulse Sp is alternately applied to the first to mth scanning/sustaining electrodes Y1 to Ym and the common sustaining electrodes Zm. Accordingly, a sustaining discharge is generated continuously only at the discharge cells formed with the wall charges by the address discharge to emit a visible light.
The AC-type PDP driven in this manner still requires to overcome several factors causing deterioration in the efficiency and the brightness. In the AC-type PDP as shown in FIG. 1, the scanning/sustaining electrode Ym and the common sustaining electrode Zm causing a sustaining surface-discharge are arranged in such a manner to be spaced at a short distance within a narrow discharge cell. When a scanning voltage pulse is alternately applied to the scanning/sustaining electrode Ym and the common sustaining electrode Zm, a discharge is initiated at a gap between the two electrodes and then a discharge area is enlarged into the surfaces of the two electrodes.
However, in such an AC-type PDP structure, since a distance between the scanning/sustaining electrode Ym and the common sustaining electrode Zm is short, a discharge path upon sustaining discharge is short to generate a small quantity of ultraviolet rays and a light-emission area within the discharge cell is extremely limited. This causes a deterioration of brightness.
Also, the AC-type PDP structure has a problem in that, as a distance between the scanning/sustaining electrode Ym and the common sustaining electrode Zm is increased so as to increase the discharge path and the light-emission area, an erroneous discharge with other adjacent cells is generated. Furthermore, a ratio of time contributing to a real light-emission in the entire sustaining interval during the sustaining period determining the brightness of the PDP is very low to cause a deterioration in the efficiency and the brightness.
A pulse width of the sustaining pulse alternately applied to the scanning/sustaining electrode Ym and the common sustaining electrode Zm in the sustaining interval SP is several μs. But, since a discharge is really generated only at a short instant supplied with a pulse, a time contributing to a real light-emission becomes merely 1 μs for each pulse. The discharge is generated once only at a very short instant for a single pulse while charged particles produced upon discharge in the remaining time are moved along the discharge path in accordance with the polarity of the electrode to form wall charges at the surface of the dielectric layer positioned at the lower portion of the electrode. Thus, an electric field at the discharge space is lowered and a discharge voltage is decreased, to thereby stop the discharge. As a result, since the major time of the sustaining interval SP is wasted for a formation of wall charges and a preparation for the next discharge, the entire sustaining interval fails to be exploited efficiently, thereby causing a deterioration in the discharge and light-emission efficiency and the brightness.